Process of refining mineral oil



; Feb. 17, 1942. J. w. POOLE 2,273,661

PROCESS OF REFIN ING MINERAL OIL Original Filed June 9, 1935 2Sheets-Sheet l Fig.1. 8%

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Feb.'l7, 1942. J w POOLE 2,273,661

PROCESS OF REFINING MINERAL OIL Original Filed June 9, 1933 2Sheets-Sheet 2 Fig 17 I F1910 Fig.

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40 S0 60 mo ZMyIhyl Ceflosolve 'ln C oTonuldehyde l n v e n Tor.

\John W. Poole b mwkw Patented Feb. 17, 1942 Substituted for abandonedapplication Serial No.

675,040, June 9, 1933. This application January 27, 1938, Serial No.187,260

7 Claims.

This invention relates to improvements in processes of refining mineraloils, and the principal object of the invention is to provide aneconomical solvent process possessing the advantages, which are inherentin an efficient solvent process, but which'is flexible and controllableto such anextent as to be universally adaptable with respect to thequality and yields of various products recoverable from. the numeroustypesof oils which are encountered in practice.

The present application is a substitute application for my applicationSer. No. 675,040, filed June 9, 1933, for Processes of refining mineraloil.

In order to accomplish thisresult it is a further object of theinvention to provide a solvent which will be sparingly soluble in theoil in order that the natural ease of solubility of the various types ofhydrocarbons and hydrocarbon derivatives present in the oil beingtreated may not be disturbed.

A further object of the invention isto provide a solvent which may beuniversally adaptable at ordinary atmospheric temperatures and pres-'sures and which will possess a proper volatility to be easily andnon-destructively removable from the oil phase.

A further object of the invention is to provide' a solvent of thecharacter above specified which when mixed with the mineral oil willefiect the formation of an oil phase and a solvent phase offsuchdifferent specific gravities that they may be readily separated.

More specifically the invention relates to a process of refining mineraloil by solvent action which comprises first preparing from known' data asolvent blend of two solvents, each sparingly soluble in said mineraloil, one possessing solvent power so great as to dissolve excessquantities of hydrocarbons of highhydrogen-carbon ratio, the otherpossessing insufiicient solvent power to properly dissolve undesirableconstituents of said oil, correlating the relative proportions of thesolvents of said blend to the temperature at which the oil is to betreated andto the qualtity or the yield of the oil phase to be produced,or to a condition intermediate of the maximum yield and the bestqualtity of the oil phase to be produced, or to the quality of theextract to be produced, second, thoroughly mixing the solvent with theoil to produce an oil phase and a solvent phase and thereafterseparating said phases and removing the solvent from the oil phase toproduce, for instance, a

lubricating oil of predetermined quality and/or" a yield or an extract.of predetermined quality.

The mathematical principles upon which the invention has: been developedare illustrated in the accompanying drawings, in which,

Fig. 1.is a graph employing the usual Cartesian coordinates illustratingdiagrammatically the mathematica} similarity of the solubility of agroup of comparatively pure hydrocarbons in all solvents in which theirsolubility is a function of temperatures;

Figs. 2, 3, 4, and 5, illustrate the effect of variouslpercentages ofwater blended with crotonaldehyde and the quality of the extract and ofthe rafiinate to such a degree as is expressed by specific gravitiesdesigned respectively as S0 for the original oil, Se for the extract,and. Sr for the raffinite, and also illustrates the corresponding effectupon the yield designated as Y. These figures vary only with respect tothe viscosity of the oil and the necessaryaccompanying characteristicsthereof Figs. 6, '7, 8, 9, and 10 (and also Fig. 3), illustrate theapproximate similarity of all solvent blends consisting of two solventseach sparingly soluble in the oil and respectively of excessive andinsufficient solvent power and demonstrate that any solvent powerintermediate of two of such selected solvents may be secured by theproper blend with the accompanying effect on yield, and thatto a; greatdegree the quality of the raflinate' and of the extract for any onesolventblend is consistent with the others for a given yield. Theapparent inconsistencies of Figs; '7 and 8-shown by the dip of the yieldcurve are in fact correlated to differences indissolved solvent.

Fig. 11 is a comparative graph showing that when a solvent not sparinglysoluble in the oil is blended with another solvent, the purpose ofmixing the solvents is frustrated by the loss of selectivity due toincreased solution in the oil; carbon tetrachloride being highly solublein oil progressively decreases. both the yield and the quality of theraflinate as its content increases in the solvent blend.

Asa result of a vast number of experiments with numerous oils andsolvents, and wide investigation of published data, I have becomeconvinced that selectivity of a solvent is brought about by two veryspecific, necessary and sulficient requirements.

First, with respect to the mixture to be separated, the solvent mustpossess a limited, although ample, solvent power for' hydrocarbons andderivatives of hydrocarbons.

separation of the two resulting phases and evapo-l rating the solventtherefrom, the desired result would be accomplished. Such a result wouldbe only possible because of the limited solvent power which caused therejection by the solvent It, therefore, followsof the desirablematerial. that limited solvent power is necessary.

On the other hand, the result would be only possible provided thesolvent possessed sufiicient solvent power to dissolve all theundesirable material present in the mixture; consequently, it is correctto say that ample solvent power is necessary. Thus the first requirementis-established.

Proof of the necessity of the second requirement and of the sufiiciencyof the two requirements may not be as simply demonstrated. If, forinstance, an unlimited amount of solvent could be dissolved in thehydrocarbon mixture it is self-evident that it would be impossible tosaturate the oil phase. With many solvents, this is essentially whathappens.

If the oil phase could not be saturated, it would be impossible to forma second or solvent phase, and if such a phase is not formed, obviouslya process dependent upon the existence of two phases cannot be employed.Even if the solvent and oil were not completely miscible, it will berecognized that if a very large volume of solvent were dissolved in thehydrocarbon mixture, such a condition would occasion the use of unusualquantities of solvent, the solvent dissolved being manifestly uselessfor extraction work, thereby producing an uneconomicalcondition.Furthermore, limited solubility in the hydrocarbon phase is necessaryfor other reasons. There is a rule of organic chemistry, used as anapproximation by physical chemists, to the effect that like dissolveslike, or in other words, the more nearly alike are two organic liquids,the more miscible will they be. It therefore follows that as more of thesolvent, which constitutes the major part of the solvent phase, becomesdissolved in the other phase, the more nearly similar will these two Hphases become, and as a consequence the more easily would all portionsof the oil phase dissolve in the solvent phase. This is graphicallyshown in Fig. 11 of the drawings.

. It therefore follows that the solvent must not be excessively solublein the hydrocarbon mixture and that the lower such solubility thegreater will be the selectivity. I havefound that given a definitehydrocarbon or even a cut of reasonably narrow boiling range, consistingessentially of members of the same hydrocarbon series, that 1 thesolubility of such material in any solvent may be expressed (withinexperimental error) by the equation:

Log Ws equals A (log TKs) in which Ws isthe amount dissolved per onehundredgrams of solvent,,T isthe absolute temperature, A is a constant,for the hydrocarbon material and Ks is a constant for a given solvent,but possessing different values for diiferent solvents.

The manner in which exact values may be predicated by the use of thisequation is shown in a paper published by me in collaboration withTheodore A. Mangelsdorf in volume 24, page 1215, of the Industrial andEngineering Chemistry, November 1932, Figure 8 of which shows theagreement between the calculated and observed values for a narrow cut ofparafiin wax.

The meaning of this equation is that if logarithmic values of solubilityare plotted on the conventional Cartesian coordinates, that solubilitytemperature curves for any one hydrocarbon-or closely related groups ofhydrocarbonswill consist'ofstraight parallel lines, one for eachsolvent, as shown graphically in Fig. 1 of the drawings. In other words,every solvent below the region of critical solution, will act exactlythe same as will any other solvent except for a temperaturecorrection.If this fact is true for all" hydrocarbonsand all pertinent dataobtained by" me confirms me in that beliefevery solvent must'at somedefinite temperature 'dissolve from any hydrocarbon mixture exactly thesame material dissolved by any one other solvent at some othertemperature. Consequently, every solvent if used at the correcttemperature would be theoretically equally selective as any othersolvent. Such variationsfrom the above rule as may occur are, in myopinion, due to the solution of the solvent in the oil phase, therebycausing the oil phase as a whole to become more and more miscible withthe solvent phase. If so, any means, such as adding a material whichwill lessen the solution in the oil phase willtend to restore the normalselective power to the solvent. If then a solvent is employed whichdissolves sparingly the oil and this solvent is thoroughly mixed with ahydrocarbon mixture, the solvent may be expected to dissolve from eachclass of compounds according to the normal solubility in such solvent.If allhydrocarbons dissolve in every solvent according to the aboveequation, it is reasonable to assume that for a given oil similarpercentages dissolved from thatoil by equal weights of solvents will beessentially alike in composition. This is graphically illustrated inFig. 1 which shows how the temperature solubility curves of differentsteps of solvents will appear whenthe logarithm of solubility and thelogarithm of temperature are plotted along-the respective coordinates. 1

, X0 represents a point of the desired solubility at temperature To. Onthe curves A, B, C, D, points Xa, Xb, X0, X1, also represent pointsofthe same desirable solubility. On the other hand, none of thesepoints-fall at the desired-temperature and will necessitate eitherrefrigeration or heating if one of the solvents to which they pertain isto be used in the process.

My work has shown'that without doubt solvents ofa group comprisingnitrobenzene, dichloro'ethylether, crotonaldehyde, ethylenedichloride,dioxan (diethyleneoxide), which may be designated as group 1, and whichare typified by thecurves C and -D-, are-solvents sparingly solublein'oil, and possess high solvent powers which will. give goodresults atthe lower temperatures, and that solvents such as acetone, acetaldehyde,water,.methyl alcohol, ethyl alcohol, and monomethyl, etherv of ethyleneglycol, etc.,,.which may be designatedas group 2, and. which aretypified by thejcurves A and B, necessitate higher temperatures topossess solvent power, X, and' na'y or v may not be satisfactory atincreased temperatures.

Therise in temperature probably will result in increased solubility inthe oil, such increase causing the solvent to be reduced in selectivity.It will in consequence be doubtful if solvents A and B can be utilizedat the temperature corresponding to Xa and Xb. Furthermore, it may notbe economical to use solvents C and D at the temperatures correspondingto X and Xd since the refrigeration required to preserve the materialsat such temperatures will often prove to be extremely expensive.

However, the problem may be considered as one in which we have, in orderto secure the proper solubility, moved these curves A, B, and C, D,respectively down or up along the temperature axis in order to causethese curves to coincide with the curve S which may be considered thecurve of the ideal solvent. Thi has been a correction by means oftemperature adjustment. On the other hand, it is possible to cause thesesame curves A, B, and C, D, to coincide with the curve S of the idealsolvent by causing them to move along the other axis, that ofsolubility, and

thereby do away with the necessity of operating likely that there willbe any increase in material dissolved in the oil. It may then bedetermined by experiment what proportion of the solvent A must be addedto solvent C to cause the curve of solvent C to coincide with the curveS.

Another and practical manner in which this operation may be regarded ithat of producing a blend of solvents A and C which will be intermediateof A and C in solvent power and if properly proportioned will coincidewith the ideal solvent S.

The above reasoning is that by which I originally arrived at aconception of the present invention.

The accuracy of the above theory has been verified byme by numerousexperiments with different solvents and with different hydrocarbon basicmaterials. In some instances apparent discrepancies have been observed,but in each case this has been found to be accompanied by either anincrease or decrease from the anticipated degree of solubility of thesolvent in the oil. This,

however, may be adjusted to approximately rethe same solvent power as ablend comprising 43% of dichloroethylether and 57% acetone. Reference tothe curve of rafiinate gravity Sr shows that the first blend will resultin a raffinate gravity of approximately .8825, whereas the second blendwill result in a raffinate gravity of approximately .8865.

Figs. 2, 3, 4, and 5, of the drawings illustrate graphically how oils ofthe samegeneral-typabut varyingzin viscosity, :may be treated by thisinvention. From these figures there may be determined the percentages ofwater and crotonaldehyde to be used in a solvent blend which will besuitable to procure a raflinate of a particular quality, and the yieldof such raffinate. These figures also show the manner in which the yieldfor eachvblend may be increased or decreased by varying the relativeproportions of the components of the solvent. Figs. 2, 3, 4 and 5 aid indetermining the proper blend of solvent to be employed which willproduce an economical balance between the quality and the yield and givea commercially desirable lubricating oil at an economical price.

Figs. 6, '7, 8, 9, and 10 illustrate the application of'the invention tooils of substantially th same basic quality derived from a common sourceand having approximately the same viscosity as demonstrated by myexperiments in which blends of different solvents were employed.

Fig. 6 illustrates the curves of the type above described resulting fromblends in different proportions of dioxan and acetone.

Fig. *7 illustrates similar curves resulting from blends in differentproportions of dichlorethylether and acetone.

Fig. 8 illustrates similar curves resulting from the use of dioxan andacetaldehyde.

Fig. 9 illustrates similar curves resulting from the use ofmonomethylether of ethylene glycol and crotonaldehyde.

Fig. 10 illustrates similar curves resulting from the use of acetone andcrotonaldehyde.

The curves illustrated herein were plotted from data actually obtainedfrom numerous experiments and the principles of the invention have beenconfirmed not only thereby, but also from data similarly obtained by theuse of other solvents .mentioned herein, together with numerous othersolvents having limited solubility in the oil treated.

Furthermore, it may be stated that with all the solvents used, I havefound that no pair of solvents having the characteristics abovedescribed failed to act within the principles herein set forth.

Ihave for a long time recognized that oxygenated compounds of lowhydrogen-carbon ratio are extremely likely to prove desirable solventsfor oil refining. Through my knowledge of this fact I have developed tothe stage of commercial utility processes using unsaturated aldehydesand their isomers which group of solvents is included in the aboveclassification of oxygenated and low hydrogen-ratio compounds, and alsocan be successfully employed in the process herein disclosed. Diethyleneoxide also falls Within the scope of I, the above classification ofsolvents,

inasmuch as it is both oxygenated and of low hydrogen-carbon ratio.

Concurrently with the general development of the invention hereindescribed, I have discovered that diethylene oxide, a commercial gradeof which has recently become available under the trade name of Dioxan,possesses proper solvent power, eifectively limited solubility in oil,proper specific gravity, and volatility as well as such othercharacteristics as are necessary for an effective selective solvent.This compound in itself apparently possesses a solvent power suitablefor many oils and in consequence may, depending on the oil to betreated, be blended eitherto increase or to decrease its solvent power.For a certain range of mineral oils, particularly neutral oils, it hasproved to be very Satisfactory without blending of any description. Itis unusually effective as a decolorizing agent. To the best of myknowledge the use of. this solvent as a selective solvent has beenheretofore unknown.

Due to the fact that a selective solvent, to be commercially useful,must conform to a number of requirements, this invention becomesparticularly important. Among the requirements which must be met by aselective solvent of commercial value for refining oils are, first, theprice of the solvent must be sufliciently low to make operation of theprocess profitable; second, the solvent must be usefully selective notfor any mixture of hydrocarbons, but for the specific mixture to beprocessed. The solvent must dissolve the undesirables and to avoiddissolving the desirable components must be sparingly soluble in them.Third, the solvent must be of such volatility as to be easily removablefrom the resulting phases, and yet not require superimposed pressure tomaintain it in a liquid state. Fourth, the compound must be reasonablystable in order to avoid loss of solvent by chemical changes. Fifth, itshould possess such specific gravity as to result in oil and solventphases easily separable each from the other.

The above discussion has stressed the fact that primarily a solvent tobe used as a refining agent must possess selectivity. This quality isprobably the most difficult of all requirements to meet.

The present invention affords an easy and inexpensive method of meetingthis requirement by the use of a considerable number of blends ofdifferent solvents.

Instances in which the quality of efficient selectivity is found withsingle solvents are comparatively rare.

In consequence, it is difiicult to select a suitable solvent which willhave all of the required characteristics to produce a proper separationof the oil into distinct phases. By this invention it is possible toselect such solvents from a comparatively large field for blending asherein described which are inexpensive, which possess the propervolatility, which are resistant to chemical changes, and which whenmixed with the oil will produce an oil and solvent phase of suchdifferent specific gravity that each will be easily separable from theother. Since for any solvent the solvent power is practically certain tobe either too high or too low for the material to be refined, theutility of the present invention is obvious. Furthermore, since mineraloil, particularly petroleum, is an extremely variable material, thesolvent power most effective for one petroleum fraction may be quiteunsatisfactory for another. From a given raw petroleum, each distillatewill vary in natural ease of solution from every other out andcorresponding cuts from different petroleums will also differ.

In the performance of the process samples are taken of the mineral oilwhich it to be treated. Two solvents, one possessing solvent powersufficiently great to dissolve excess quantities of hydrocarbons of highhydrogen-carbon ratio, and the other possessing insuflicient solventpower to properly dissolve undesirable constituents of the oil, are thenblended in such proportions as to produce a proper solvent value at adesired temperature and the quality of the oil and yield noted.Different solvents of high and low solvent power may be compared todetermine the best to be employed in the process. When a proper solventsolution is obtained the relative values may be plotted on Cartesiancoordinates as heretofore described and the relative proportions of theconstituents of the blended solvents can thereupon immediately bedetermined by reference to the chart to produce a desired quality or adesired yield, or a commercial valuable condition of quality and yieldintermediate of the best quality, and the maximum yield.

It has heretofore been stated that the object of the invention is toprovide a solvent which at ordinary atmospheric temperatures andpressures will possess proper volatility to be easily andnon-destructively removed from the oil phase, and that the solventsemployed are blended in such proportion as to produce a, proper solventvalue at a desired temperature and the quality of the oil and yieldnoted in the manner above specified. It is of course understood that itis not feasible to permit a solvent blend to fluctuate in temperatureaccording to diurnal fluctuations of temperature or even to fluctuationsover somewhat greater periods and that if a temperature of, for exampledegrees F. is once arrived at and imposed by atmospheric conditions,that approximately such temperatures will in all likelihood benecessarily maintained in the solvent blend. If temperatures wereallowed to fluctuate according to diurnal fluctuations, it is evidentthat it would be constantly necessary to alter the composition of thesolvent blend utilized.

For example, if the greatest atmospheric temperature reached undersummer conditions were to be F., it is quite reasonable to believe thateconomics would requir operation at that certain temperature. Choosingsuch a temperature would avoid the necessity of resorting torefrigeration to maintain constant conditions within the system and heatexchange apparatus could be simplified to the extent that only a smallamount of heating would be required.

By the use of my invention a proper blend of selected solvents may beemployed to produce a predetermined raffinate, extract, or yield, or adesirable product intermediate of maximum quality and maximum yield.Furthermore, by my invention, use may be made of two solvents which intheir pure state would be valueless for commercial operation, in thatone might possess extremely great power to dissolve hydrocarbons and theother insufficient power to dissolve the undesirable compounds, whilethe blend of two of such solvents in the manner above described would besatisfactory.

Another advantage of the present invention in control of solvent powerlies in the fact that it is frequently desirable to produce more than asingle pair of products from a specific raw material; for example, itmay be that on occasions it is desirable to improve a Mid-Continent oilto the point Where it meets the specifications for Pennsylvania oil, oran oil which is extremely light in color. In such cases it is usuallynecessary to remove more material than when merely desiring to producean oil of proper color, carbon residue and emulsion tests. Suchdifferences in dissolved quantities necessitate different solvent powerswhich may be obtained by adjusting the relative proportions of suitablemixed solvents.

A specific illustration which has been effected is as follows:

Certain Mid-Continent neutral oil of approximately 250 Saybolt Universalviscosity at F. was found to possess considerable quantities of materialsimilar to Pennsylvania oil and also Approximatc.

a =la-rge volume of oil much-like so cajlled' Coastal on. It alsocontained theflusualdeleterious matter detrimental to all highergrade-oils Because of -move nearly 50% of the total mas er ,Inthis "casethe raw 'stock was first treated with a solvent blend oi highsolventpowercomprising {33% crotonaldehyde and- 17% acetone inaccordance withtheprinciples of th'e presentinvention; The

solvent was evaporated from thesolv'ent phase av n n a to app atel 4 othl extracted with a solvent blend similar tothe firstexceptthat'waterwas added to decrease itsmiscibi'l ityand solvent'power.As a result nearly allot "the originally extracted material was.jrecovere'd as'a commercial on. of the Coastal type. 'The Of theproducts thus produced a large amount of the more valuablePennsy-lvaniatype of oil was-obtained, as well as--oil' -o'f the Coastal type whichis also a valuablef commercial product. Even the heavy extract'isvaluable asa'lubrict'nit for slow moving machinery, or asa rawmaterialfor the production of high anti-knockgasoline. i

The process above defined was performed at a uniform temperature of 63F., whereas if a pure solvent, such as crotonaldehyde, had beenemployed, the original extraction would necessarily have been made atapproximately 32 F., and the secondary extraction at approximately 0 F.,if it could have been made at all.

In view of the fact that at'60 F. all solutions are very fluid andseparation easily effected, difficulties of separation caused by lowtemperatures may be avoided by the present invention.

My invention has been found to possess utility at temperatures somewhatgreater than those normally imposed by atmospheric conditions in thecase of waxy or viscous oils. For example, processing a heavylubricating stock which after extraction produced a rafiinate of 120 F.pour point, it was found that settling and general mechanical operationwas greatly improved if a temperature in the region of 130 F. weremaintained in the final stages of countercurrent apparatus. Due to thissomewhat elevated temperature, the solvent which at normal atmosphericconditions possessed a desirable solvent power was found to be toomiscible with the oil phase and in consequence a greater amount ofsolvent of insufficient solvent power proved necessary. However, byproperly proportioning the solvent blend, it was possible to producesuch a blend to provide an efiicient and economical extracting agent.

While in the foregoing disclosure reference is made to the use of twosolvents having the respective characteristics herein described, it willbe understood that one or both of the solvents may be a solvent mixtureor blend having the characteristics above described as exemplified inthe treatment of the Mid-Continent stock above described.

original amount, This extract, obviously eing highly miscible in theoriginal solvent blend was It will be understood that the present tionin its broad aspect comprises the use of any solvent or solvents havingthe characteristics herein described and used in the performance of theprocess as 'herein s et forth within the meaning and scope of thefollowing claims' Iclaim: Y 7 L'The process of refining a mineraloil'containing desirablelubricating oil by selective solvent action ofsuitable solvents substantially liquid at usual atm'ospheric conditionsunder which conditions none of' thesolvents used will by itself approachmaximum selective efi'iciency 'which comprises using as a solvent ablend of crotonaldehyde and another .solvent which is sparingly solublein said mineral 0i1, ,is substantially liquid under said conditions, andpossesses insufficient solvent power to properly dissolve hydrocarbonsof low hydrogen carbon. ratio of said oil under said conditions, therelative proportions of the blended solvents being correlated .to thenature of the oil being treated. and to said c'onditionsto cause theresultant blend .to possess av solventpower of approximate maximum.selec-' .tive eflicieney intermediateof the solvent powers of therespective solvents, contacting the solvent blend with the oil toproduce a fluid oil'phase and a fiuid solvent phase, thereafterseparating the phases andremoving the solvent fromthe oil phase toproduce a lubricating oilof (predetermined quality and yield. I I I 2.The process of refining a mineral oil containing desirable lubricatingoil by selective solvent actionof suitable. solvents'substantiallyliquid at usual atmospheric conditions under Iwhich conditions noneofthe solvents used will by itself approach maximum selectiveefii'cienoy which comprises using as va solvent a blend ofcrotonaldehyde and water, the relative proportions of the blendedsolvents being correlated to the nature of the oil being treated, and tosaid conditions to cause the resultant blend to possess a solvent powerof approximate maximum selective efiiciency intermediate of the solventpowers of the respective solvents, contacting the solvent blend with theoil to produce a fluid oil phase and a fiuid solvent phase, thereafterseparating the phases and removing the solvent from the oil phase toproduce a lubricating oil of predetermined quality and yield.

3. The process of refining a mineral oil containing desirablelubricating oil by selective solvent action of suitable solventssubstantially liquid at usual atmospheric conditions under whichconditions none of the solvents used will by itself approach maximumselective efficiency which comprises using as a solvent a blend ofcrotonaldehyde and 'acetaldehyde, the relative proportions of theblended solvents being correlated to thenature of the oil being treated,and to said conditions to cause the resultant blend to possess a solventpower of approximate maximum selective efiiciency intermediate of thesolvent powers of the respective solvents, contacting the solvent blendwith the oil to produce a fluid oil phase and a fluid solvent phase,thereafter separating the phases and removing the solvent from the oilphase to produce a lubricating oil of predetermined quality and yield.

4. The process of refining a mineral oil containing desirablelubricatingoil by selective solvent action of suitable solvents substantiallyliquid at usual atmospheric conditions under which conditions none ofthe solvents used will by itself approach maximum selective efficiencywhich comprises using as a solvent a blend of crotonaldehyde andacetone, the relative proportions of the blended solvents beingcorrelated to solvent blend with the oil to produce a fluid oil phaseand a fluid solvent phase, thereafter separating the phases, andremoving the solvent .from the oil phase to produce a lubricating oil ofpredetermined quality and yield. 5. The process of refining mineral oilcontaining desirable lubricating oil to produce a lubri-' eating oil-,of predetermined quality and yield, by selective solvent action ofsuitable solvents substantially liquid at usual atmospheric conditions.under which conditions none of the solvents used will by itselfapproach maximum selective efiiciency which comprises using as a solventa mutually soluble blend of an unsaturated aldehyde having the essentialsolvent properties of crotonaldehyde and another solvent which issparingly soluble in said mineral oil, is substantially liquid undersaid conditions, and possesses insuficient solvent powerto properlydissolve hydrocarbons of low hydrogen-carbon ratio of said oil undersaid conditions, the relative proportions of the blended solvents beingcorrelated to the nature of the oil being treated, and to saidconditions to cause the resultant blend to possess a solvent power ofapproximate maximum selective efiiciency intermediate of the solventpowers of the respective solvents, contacting the solvent blend with theoil to produce a fluid oil phase and a fluid solvent phase, thereafterseparating the phases, and removing the solvent from the oil phase toproduce a lubricating oil of predetermined quality and yield.

6. The process of refining hydrocarbon oil containing constituents oflow and high hydrogencarbon ratio by selective solvent action ofsuitable solvents substantially liquid at usual atmospheric conditionsunder which conditions none of the solvents used will by itself approachmaximum selective efficiency which comprises extracting the oil with anunsaturated aldehyde as a primary selective solvent having the essentialsolvent properties of crotonaldehyde under said conditions in thepresence of a secondary solvent which is sparingly soluble in said oiland is adapted to reduce the solvent capacity of said primary solventfor said constituents of high hydrogen-carbon ratio, the relativeproportions of the primary and secondary solvents being correlated tothe nature of the oil being treated and to the conditions of operationto cause the resultant blend to possess a solvent capacity of aproximate maximum selective efilciency intermediate of the solventcapacities of the respective solvents, forming a fluid oil phaseincluding oil constituents primarily of high hydrogen-carbon ratio and afluid solvent phase including oil constituents primarily of lowhydrogen-carbon ratio, and separating the said phases.

'7. The process of refining a mineral oil as defined by claim 4 in whichthe solvent is removed from the solvent phase to leave an oil extract,and re-extracting said extract with a blend of crotonaldehyde, acetoneand Water to produce a lubricating oil therefrom.

JOHN WARD POOLE.

